The invention relates to a molding compound according to the generic part of claim 1 and its use for elastic clamp-proof courses as well as to its use for elastic sealing strips.
Strip and foil material for providing seals in building construction, underground structures and engineering work must possess a series of different properties to ensure that structures remain watertight and weatherproof. These properties include high mechanical strength and adequate elongation both at room temperatures and at temperatures of up to about 80.degree. C., long-term stability, the ability to join large areas to each other, resistance to aging and biological resistance. Sealing strips varying widely in composition, based upon thermoplastic synthetic materials, vulcanizable or vulcanized elastomers, and thermoplastic synthetic materials having elastomeric properties are already known, but although they have advantageous properties, they also have disadvantages (see for example: DE-AS 15 70 352, DE-AS 15 95 442, DE-OS 22 19 147, DE-24 10 572-A1, DE-24 15 850-A1, DE-25 10 162-A1, DE-26 21 825-B2, DE-26 28 741-A1 and DE-26 57 272-A1).
Although known thermoplastic sealing strips, based for example upon plasticized polyvinylchloride, polyisobutylene, acrylic polymers, or thermoplastics modified with bitumen may be simply and effectively welded to seams, they are sensitive to the effects of temperatures. Attempts are made to counteract these disadvantages by coating or incorporating fabrics or fleeces made of textile or glass fibers, but this has been only partly successful.
Although known sealing strips made of vulcanizable synthetic materials, e.g. based upon chloroprene rubber, ethylene propylene diene terpolymers, chlorosulfonated polyethylene rubber, or butyl rubber meet mechanical strength requirements at room temperature and are weatherproof, they have considerable disadvantage, however. Unvulcanized foils (e.g. EP-OS 0 082 490) do not meet mechanical demands at elevated temperatures and vulcanized sealing strips cannot be welded together, but can be permanently joined together only with difficulty by means of adhesive, adhesive tape or the like (see for example DE-OS 25 10 162).
There has recently been a change from the plastic sealing strips described hereinbefore, made of a single layer of one material, possibly with a reinforcing insert, to multilayer sealing strips made of vulcanizable materials. The outer layers are either unvulcanized or are vulcanized only to the extent that they can be welded by heat, by a solvent, or by a solvent welding agent, and at least one vulcanized layer is provided, see for example AT-PS 290 612 and DE-OS 26 28 741. The disadvantage, however, is that the process is dependent upon the type and amount of vulcanizing accelerator used and the time required for complete vulcanization.
DE-OS 22 19 147 discloses a sealing strip based upon EPDM. In addition to EDPM it contains polyethylene, polyisobutylene and fillers. At room temperature the elongation at rupture amounts to between 500 and 600%. At elevated temperatures such foils exhibit very low tensile strength and elongation at rupture.
DE-OS 24 10 572 discloses a sealing strip based upon polystyrene polybutadiene block copolymers having a greater elongation at rupture of max. 210% at 80.degree. C. Such foils have unsatisfactory resistance to light and ozone.
Also known from DE-OS 26 21 825 is a sealing foil based upon polystyrene polybutadiene block copolymers with additions of chlorosulfonated polyethylene with very high elongation at rupture up to 660% at 80.degree. C. However, when fillers are added, this value drops to less than 300%. It may also be gathered from this reference that the addition of polyethylene instead of chlorsulfonated PE produces poor elongation at rupture at 80.degree. C.
DE-OS 26 57 272 discloses a thermoplastic compound for sealing foils. For the purpose of achieving satisfactory strength at elevated temperatures, this compound contains, in addition to 100 parts by weight of EPDM, between 50 and 150 parts by weight of a polyethylene having a melt flow index - MFI- (190/2.16) of between 0.2 and 50 g/10 min, and between 30 and 150 parts of carbon black and possibly bitumen, mineral oil, chalk and lubricants. These foils exhibit tensile strengths of up to 4.7 N/mm.sup.2 and elongations at rupture of up to 420% at 70.degree. C.
These mechanical values are inadequate for many practical applications. For instance, strips according to DE-OS 26 57 272 achieve elongations at rupture in excess of 300% only if they contain large amounts of polyethylene.
Sealing strips made of molding compounds containing large amounts of PE are so stiff that they cannot be used for roof sealing.